We propose to utilize the knowledge and expertise we have acquired in our ongoing studies of viral-keratinocyte interactions to explore the use of keratinocytes as vehicles for gene therapy. Many of the potential complications associated with the use of marrow cells in gene therapy would be reduced or eliminated with the use of genetically altered keratinocytes. What is needed for a proper consideration of this concept is an understanding of exogenous gene expression in keratinocytes. Preliminary studies have shown that high level transient expression of the gene for chloramphenicol acetyltransferase is possible in cultured epidermal keratinocytes following DNA-mediated gene transfer. In this proposal, we have set forth experiments with cloned genes and cultured human epidermal keratinocytes that are designed to (1) explore the use of calcium phosphate cotransfection and an adenovirus vector system as methods to achieve stable gene transfer and expression, (2) examine the effect of keratinocyte differentiation on exogenous gene expression, (3) investigate the effect of exogenous gene expression upon the growth and differentiation of the genetically-transformed keratinocyte, (4) explore the possibility of using a segment of adenovirus in the construction of a differentiation-activated expression vector, and (5) determine, with an experimental animal model, if genetically altered keratinocytes are a feasible means of administering gene therapy. In addition to providing vital information on the possibility of using keratinocytes for gene therapy, these studies will continue to help us gain an understanding of how keratinization in oral mucosa and epidermis is regulated.